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Although global warming is driven by human behaviour – and in particular the prodigal burning of fossil fuels at an ever-accelerating rate to dump ever-greater quantities of carbon dioxide in the atmosphere – it is also influenced by natural climate rhythms.

And, say scientists from Australia’s Centre of Excellence for Climate System Science, one of these is a slow-moving oceanic and atmospheric cycle called the Interdecadal Pacific Oscillation (IPO), which blows hot and cold and then hot again, every decade or so.

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If the world is to have any hope of meeting the Paris targets, governments will need to pursue policies that not only recuce emissions but remove carbon dioxide from the atmosphere. magna lorem ipsum dolor sit amet, consectetur adi

Ben Henley, lead author, University of Melbourne

Global records

But the last three years have all breached successive global temperature records, and they think this could mean that the IPO is beginning to have a positive effect.

“Even if the IPO remains in negative phase, our research shows we will still likely see global temperatures break through the 1.5°C guardrail by 2031,” says Ben Henley, of the University of Melbourne, who led the study.

“If the world is to have any hope of meeting the Paris targets, governments will need to pursue policies that not only reduce emissions but remove carbon dioxide from the atmosphere”.

“Should we overshoot the 1.5°C limit, we must still aim to bring global temperatures back down and stabilise them at that level or lower.”

Carbon dioxide levels for most of human history oscillated at around 280 parts per million. Since the beginning of the Industrial Revolution, they have risen inexorably, to reach 400ppm.

Global average temperatures have crept up to almost 1°C higher than the historic levels. In fact, the Paris Agreement talked of aiming to keep them “well below 2°C”, but 1.5°C has always been an ideal limit.

Dr Henley and his co-author are not the only scientists to cast doubt on the world’s capacity to achieve the Paris promise. Two of the giants of climate science pointed out within a month of the historic decision that current greenhouse gas emissions would take the world to the 2°C target very swiftly.

So although the latest warning from Australia sounds ominous, it is consistent with other thinking. The nations that signed up to the Paris accord have – mostly – made declarations of their plans to reduce emissions, but many of these have yet to be implemented and in any case are widely understood to be insufficient.

So the Melbourne study could best be considered as yet another reminder of the urgency of international action.

Although the Earth has continued to warm during the temporary slowdown since around 2000, the reduced rate of warming in that period may have lulled us into a false sense of security. The positive phase of the IPO will likely correct this slowdown. If so, we can expect an acceleration in global warming in the coming decades,” Dr Henley says.

“Policymakers should be aware of just how quickly we are approaching 1.5°C. The task of reducing emissions is very urgent indeed.”

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